I know there's a lot of archived oppinion on this, but has anyone with an '85 C4 L98 removed either the first or second screen and what results did you notice if any?

I understand the screens main role is to 'straighten' air flow across the sensor wire, but does removing the second screen closest to the TB change anything or is it there to help with the straightening effect?

:cheers:

 

I just modified the reman bosch maf I bought last month and removed the screens. (Left the heatsinks in there). I am planning to do a dyno run again in a week or two to see if I gained anything just by that.
Theoritically a little bit at higher rpms, yea.

I remember removing the screens and gutting the maf's heatsinks years ago and I do recall better acceleration, but who knows..

 

I did mine a couple years ago...and I can't honestly say there was any "seat-of-the-pant" improvement. I would be interested to see what the dyno before/after results are though.

 

Did you remove BOTH screens?

Was there any change to idle or normal driving as in erratic running or hunting?

 

I just removed mine on my 86. Seems to be just fine. It sertainly didnt hert

 

Ok.. lemme see if I can put my engineering degree to use here. It hasn't helped much anywhere else! :jester

It is true that the first screen 'straightens' flow. Sorta. By introducing this restriction across the entire flowpath, the formerly developed boundary layer is disrupted. This means, that the incoming air velocity across the entire cross section (after the screen) is more balanced. Before the screen, the air velocity near the walls was significantly lower than the air velocity in the middle of the intake duct. After the screen, this will still be the case, but to a lesser extent.

So... without the front screen in, I can safely say that the MAF wires will see a higher air velocity (since they're in the center of the duct). Which means, the MAF wires exchange heat faster, and take more current to maintain their temperature value. So... the computer thinks more air molecules are entering the engine, and reacts by putting more fuel in. Obviously flow is improved with the screen out, so more air enters the engine, but the MAF will be tricked to some extent beyond the actual flow by removing the front screen.

I'm not tryin to pull some b.s. here, this makes sense to me! But as always, I'm open to criticism, unless you disagree with me! :D :lol:

As for the back screen, I can't see how it'd have any affect on the MAF or engine other than the flow restriction. It should always be removed. :yesnod:

 

Thanks for your in depth reply my friend!
OK, I'm sort of convinced to at least remove the rear screen when I return from a long run at the end of the week.

I just thought MAYBE the rear served a purpose too;

as in, imagine two people holding a rope between them, going thru a hoola-hoop (GOD I'm OLD!) without the person at the rear holding it straight, it wouldn't BE straight...get my scenario?

Obviously that doesn't apply then? According to your theory; once the 'steadied' air has passed the sensor wire, the vortex returns, correct?

:eek:

 

rip 'em out :yesnod: :cheers:

 

The 85 MAF is different than the 86-89 models. The screens don't just pop out. It's metal screens that are sandwiched right between the plastic, so you need to physically cut them out. I cut them out of mine and noticed a whole lot of no difference.

 

'Tis true, if it is an original GM non reman unit.
I picked up a reman for my '85 last month, and the screens popped out very easily. Nothing needed to be cut. I can put them back if I ever want to warranty exchange it. :D

 

I removed both screens and cut back the heat sink fins on my 87 and didn't notice any real difference. I know there have been sensible educated comments about the effects of screen removal and its effect on the MAF calibration, but I think you need to look at the whole package.
At part throttle (closed loop), several sensors come into play. Throttle position, MAF & Oxygen sensor/s. There are others as well. If there are any changes at part throttle due to the MAF mods/changes, the O2 sensor should pick this up and trim fuel injection pulse width accordingly. At WOT, (open loop)TPI engines as do most others have a tendency to run a little rich, due to the engine using a set of calibrations pre set in the ECM. 'Gutting the MAF' usually I believe has a tendency to lean the mixture slightly, potentially giving a performance advantage. However on a stock car it isn't very noticeable. there is potential for more power due to more airflow, but with the tpi already being strangled in stock form at the manifold it is probably very slight. A properly fitted air filter should give adequate protection from debris. This is purely my own opinion which is not based on any dyno experience just my butt. Maybe someone has dyno info to offer. :steering:

 

I removed both screens and the heat sink. No problems at all. Not enough of a difference to feel, but it's free :cheers: .

 

I took both out. Might make a bit of difference. I dont think enough to really matter. I guess if you are racing every little bit helps. :seeya

 

Of course an engineer may trump IMHO degree but here goes. If the MAF works on the principal of cooling the wire than MORE air would equal MORE cooling no matter how straight it is. Bachelors of IMHO degee. :crazy:


[Modified by Southern Comfort, 4:06 PM 8/20/2003]

 

OK folks; I did it!

I pulled out the rear screen today (Carefully with pliers!) and I TOO notice no difference at all.

I ALSO left in front screen as I ALWAYS notice a small bug on it. so yes, I guess the protection factor is worth more than the .000001 % airflow gain!

Thanks all for your input.


PS If I take out the stuffed front right BOSE speaker from my door, I think I'll gain more HP from the weight saving than I did from screen removal!

:cheers: :withstupid:

 

When I put the 1000 cfm MAF ends on (they are plastic) I took the screens off the old ends, and shoved them into the new ones. A little melting from a soldering iron and "TA DAAA!" one protected MAF sensor.

I've pulled too many moths and bugs (I don't know how they got in there either) out of those screens to ever leave them off!

If you want more HP, buy some mods that are proven to work! Just look @ my sig! :thumbs:

 

If you consider that the MAF is just one piece of the induction system. And if you apply that age old axiom "A chain is only as strong as it's weakest link" then of course you can't expect large gains from removing the screens alone... Other mods are necassary to compliment the increased airflow. If intake flow is increased exhaust flow must be similarly increased.

The MAF end screens and internal heat sink fins limit maximum air flow.
529 CFM - max. flow rate stock
711 CFM - max. flow rate with screens removed
750 CFM - max. flow rate with screens and cooling fins removed
Reference - TPIS "Insider Hints", pp 10.

I cut the screens out but left the heat sinks intact and gained much by the SOTP dyno. MAF screen removal was the last of these mods...

Open the air cleaner lid, K&N Air Filter, set TPS voltage to .62, gutted the cat, 40 series Flowmasters, cut back plugs, and then descreened the MAF. Haven't installed the AFPR yet. Waiting til I have the time to port match the TB, plenum, runners and intake all at once.

I endorse removing the screens. :seeya

 

No Noticable difference :nonod:

 

...So how many CFM gain for just the rear screen removed?

 

On my 85 I took out both screens and the heat sinks, as a result of the TPIS claims.

my HP went form 230HP up to @ 400HP,,,,, or,,,,,, maybe that was the new 406 engine that gave me the increase:D